System level evaluation of UL and DL interference in OFDMA mobile broadband networks

Abstract

-This paper presents results from a novel OFDMA multi-cell mobile broadband system level simulator. The tool is used to statistically characterize uplink and downlink inter-cell interference. Without suitable interference management, multi-billion dollar networks can collapse under the strain of heavy traffic loads. Fully loaded interference studies cannot be performed on the network until it has been fully deployed. As such, interference analysis and management must be accurately performed pre-deployment using detailed network simulators. System level simulation is a highly computationally intensive procedure. This paper discusses the simulator architecture (and steps taken to reduce computational complexity) and then demonstrates the impact of inter-cell interference in OFDMA networks. In an interference limited scenario the results demonstrate that it is the frame-to-frame fluctuations in interference, and not the received signal level, that dominate inaccuracies in the Channel Quality Index (CQI) prediction. CQI is used in the fast link-adaptation process to select the MCS mode for each user on a frame-byframe basis. Results show that incorrect Modulation and Coding Scheme (MCS) modes are chosen up to 40% of the time when the CQI is delayed by 3 frames and the user is interference limited. Perfect MCS selection is then shown to improve user throughput by up to 50%.

Massive MIMO real-time channel measurements and theoretic TDD downlink throughput predictions

“…This technique is fully described in [14] and the references therein, and was also used in [15] and [16]. Without sacrificing accuracy, the runtime of the RBIR simulations is many hundreds of times faster than full bit-level simulation.…”

Comparing Theoretic Single-User and Multi-User Full-Dimension MIMO Data Throughputs in Realistic City-Wide LTE-A Deployments

“…This technique was fully described in [15] and subsequently used in a number of our Wireless LAN and cellular network studies, for instance [21] and [22]. Without sacrificing accuracy, abstraction is many hundreds of times faster than full bit-level simulation.…”

“…Section III explains our 3D channel propagation modelling process. Section IV introduces our LTE-A DL network simulator with EBF and BD precoding methods, as well as the associated RBIR (the Received Bit level mutual Information Rate) abstraction technique [15]. Simulation results in the form of expected user throughput, statistics for the number of supported spatial streams and outage probabilities are given in Section V. Finally, Section VI summarises the comparison of large-scale 3D SU and MU MIMO for heterogeneous LTE-A deployment.…”

Codebook based beamforming and multiuser scheduling scheme for mmWave outdoor cellular systems in the 28, 38 and 60GHz bands

“…For link level analysis, the system throughput was estimated using a state-of-the-art Received Bit Mutual Information Rate (RBIR) abstraction technique that is fully described in [15] and extensively used in [16]. This approach can be used as an alternative to bit-accurate PHY layer simulation which becomes time prohibitive when applied to system level (multi-user) applications with large combinations of MCS mode, antenna type and orientations [17].…”